The Effect of Bubbling and AlCuP for Refining Primary Silicon at Al-18%Si Alloy

2007 ◽  
Vol 124-126 ◽  
pp. 1489-1492
Author(s):  
Jung Pyung Choi ◽  
Won Jung Kim ◽  
Tae Woon Nam ◽  
Eui Pak Yoon
Keyword(s):  
Primary Silicon ◽  
Nucleation Site ◽  
Optimum Treatment ◽  
Primary Si ◽  
Nucleation Sites ◽  
Stirring Time ◽  
Holding Temperature ◽  
Treatment Order

This paper investigates the effect of Bubbling and AlCuP on primary Si size in Al-18%Si alloy. Bubbling process and AlCuP treatment are effective for refining primary Si in hypereutectic Al-Si alloy. Both the bubble and AlCuP can be used as nucleation sites of primary Si. Many nucleation sites can make the size of primary Si decreased. So, this experiment suggests that the mix using of bubbling process and AlCuP treatment are more effective for nucleation site of primary Si. For deciding the optimum treatment order, the experiments are processed 3 kinds of order with varying stirring time and holding temperature; 1)AlCuP treatment and then bubbling process, 2)simultaneously using of bubbling process and AlCuP treatment, 3)bubbling process and then AlCuP treatment.

Effect of Bubbling on the Primary Silicon in Hypereutectic Al-Si Alloy

2004 ◽  
Vol 449-452 ◽  
pp. 153-156 ◽  
Author(s):  
Jung Pyung Choi ◽  
Sang J. Lee ◽  
Eui Pak Yoon ◽  
W.Y. Yoon ◽  
M.H. Kim ◽  
...  
Keyword(s):  
Bubble Size ◽  
Processing Time ◽  
Primary Silicon ◽  
Water Model ◽  
Primary Si ◽  
Nucleation Sites ◽  
Holding Temperature

This paper investigates the effect of bubble on the primary Si size in Al-18wt.%Si alloy. The primary Si size observed was varied with bubble size and bubbling time in bubble process. The effect of the holding temperature of the melt in bubbling process was also investigated. In water model, as the injecting bubble size decreases, the residual bubble size in the water decreases and the residual bubble conservation time in the water increases. Also in the experiment of Al melt, the primary Si size decreases, as the injecting bubble size decreases and as the bubble processing time increases. Pore was observed at the center of primary Si. This pore was observed at many Si phases. So, this experiment suggests that the bubble can be used as nucleation sites of primary Si.

scholarly journals Simultaneous Refinement of Primary Si and Modification of Eutectic Si in A390 Alloy Assisting by Sr-Modifier and Serpentine Pouring Channel Process

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3109 ◽  
Author(s):  
Pengyu Yan ◽  
Weimin Mao ◽  
Jing Fan ◽  
Bingkun Wang
Keyword(s):  
Eutectic Silicon ◽  
Primary Silicon ◽  
Interface Energy ◽  
Nucleation Site ◽  
Nucleation And Growth ◽  
Dominant Factor ◽  
Channel Process ◽  
Primary Si ◽  
Eutectic Si ◽  
A390 Alloy

In this study, A390 alloy was prepared using the combined process of a water-cooled copper serpentine pouring channel (SPC) and strontium (Sr) modifier, in order to simultaneously refine primary silicon (Si) and modify eutectic silicon (Si). The nucleation and growth mechanisms of the Si phase were discussed by morphology analysis and non-isothermal analytical kinetics. The results indicate that the size of primary Si is refined to 25.2–28.5 µm and the morphology of eutectic Si is modified from acicular into fibrous. The serpentine pouring channel process stimulates primary Si nucleation due to chilling effect and has no influence on eutectic Si nucleation. Impacts of Sr-modifier on primary and eutectic Si are similar, including three aspects: (1) poisoning of the nucleation site; (2) decreasing the interface energy between Si phase and liquid; (3) raising the activation energy for diffusion across solid-liquid interface. The content of Sr determines which one of the three aspects mentioned above is the dominant factor to promote or restrain the nucleation and growth of the primary and eutectic Si in hypereutectic Al-Si alloy.

Proton Induced Structuring of a Photostructurable Glass

2002 ◽  
Vol 739 ◽  
Author(s):  
Meg Abraham ◽  
Inmaculada Gomez-Morilla ◽  
Mike Marsh ◽  
Geoff Grime
Keyword(s):  
Three Dimensional ◽  
Particle Beam ◽  
Nucleation Site ◽  
Buried Structures ◽  
Corning Glass ◽  
Nucleation Sites ◽  
Initial Nucleation ◽  
Similar Product ◽  
Photon Process ◽  
Meta Silicate

ABSTRACTThe use of photons to create intricate three-dimensional and buried structures [1] in photo-structurable glass has been well demonstrated at several institutions [2]. In these instances the glass used whether it be Foturan™, made by the Schott Group or a similar product made by Corning Glass, forms a silver nucleation sites on exposure to intense UV laser light via a two-photon process. Subsequent annealing causes a localized crystal growth to form a meta-silicate phase which can be etched in dilute hydrofluoric acid at rates of 20 to 50 times that of the unprocessed glass. The same formulation of glass can be “exposed” using a particle beam to create the nucleation site. In the case of particle beam exposure, experiments have shown that the mechanisms that cause this initial nucleation and eventual stochiometric transformation, after annealing, depend largely on the beam energy.

Carbon Black and Fullerenes: New Discoveries in Early Formation Mechanisms and Nucleation

2000 ◽  
Vol 73 (5) ◽  
pp. 875-888 ◽  
Author(s):  
M. Pontier Johnson ◽  
R. W. Locke ◽  
J. B. Donnet ◽  
T. K. Wang ◽  
C. C. Wang ◽  
...  
Keyword(s):  
Carbon Black ◽  
Mass Spectroscopy ◽  
Photoelectron Spectroscopy ◽  
Nucleation Site ◽  
Formation Mechanisms ◽  
Clear Understanding ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Buckminster Fullerene ◽  
Secondary Ion

Abstract Recent studies on the formation of carbon black have resulted in the previously unreported finding of buckminster-fullerene, C60, in trace quantities in the toluene extractable materials. High-resolution transmission electron microscopy (HRTEM) experiments indicate the molecule may be functioning as a nucleation site in the formation of primary particles of carbon black. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) provided the surface chemical analysis of conventional and experimental carbon blacks. The toluene extracts represented the precursor compounds present in the gaseous phase at the time of quench. The extracts were analyzed by Fourier transform infrared (FTIR) spectroscopy, liquid chromatography (LC)/mass spectroscopy (MS) and elemental composition. The data, taken as a whole, have led to a more clear understanding of the competitive chemical pathways occurring during the inception and nucleation of a primary particle of carbon black. Direct observation of nucleation sites and types are possible with HRTEM analysis.

scholarly journals Ice nucleation efficiency of clay minerals in the immersion mode

2012 ◽  
Vol 12 (13) ◽  
pp. 5859-5878 ◽  
Author(s):  
V. Pinti ◽  
C. Marcolli ◽  
B. Zobrist ◽  
C. R. Hoyle ◽  
T. Peter
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Differential Scanning Calorimeter ◽  
Pure Water ◽  
Nucleation Site ◽  
Ice Nucleation ◽  
Nucleation Sites ◽  
The One ◽  
Site Classes

Abstract. Emulsion and bulk freezing experiments were performed to investigate immersion ice nucleation on clay minerals in pure water, using various kaolinites, montmorillonites, illites as well as natural dust from the Hoggar Mountains in the Saharan region. Differential scanning calorimeter measurements were performed on three different kaolinites (KGa-1b, KGa-2 and K-SA), two illites (Illite NX and Illite SE) and four natural and acid-treated montmorillonites (SWy-2, STx-1b, KSF and K-10). The emulsion experiments provide information on the average freezing behaviour characterized by the average nucleation sites. These experiments revealed one to sometimes two distinct heterogeneous freezing peaks, which suggest the presence of a low number of qualitatively distinct average nucleation site classes. We refer to the peak at the lowest temperature as "standard peak" and to the one occurring in only some clay mineral types at higher temperatures as "special peak". Conversely, freezing in bulk samples is not initiated by the average nucleation sites, but by a very low number of "best sites". The kaolinites and montmorillonites showed quite narrow standard peaks with onset temperatures 238 K

A Fluorescence Assay for DNA with Covalently Linked Complementary Sequences

1972 ◽  
Vol 50 (2) ◽  
pp. 210-216 ◽  
Author(s):  
A. Richard Morgan ◽  
Verner Paetkau
Keyword(s):  
Ethidium Bromide ◽  
Fluorescence Enhancement ◽  
Nucleation Site ◽  
Heat Denaturation ◽  
Heating And Cooling ◽  
Physical Measurements ◽  
Complementary Sequences ◽  
Naturally Occurring ◽  
Nucleation Sites ◽  
Covalently Linked

An assay which measures polydeoxyribonucleates containing covalently linked complementary sequences is described. It is based on the fluorescence enhancement of ethidium bromide bound to bihelical polydeoxyribonucleates. This dependence of fluorescence enhancement upon bihelicity has been further documented. Synthetic, defined polymers, such as d(A)n∙d(T)n, d(AT)n∙d(AT)n, d(TC)n∙d(GA)n, and d(TTG)n∙d(CAA)n, have been studied, as well as naturally occurring DNAs. At moderate ionic strengths, the synthetic polymers will re-anneal following heat denaturation. Their facility to renature is due to the self-complementarity between strands throughout their lengths. This facility is lost at very low ionic strengths (Γ/2 < 0.003 M), where ionic repulsion prevents the formation of "nucleation" sites for annealing. However, a covalent linkage between strands provides a nucleation site for renaturation. The fluorescence seen with ethidium bromide after heating and cooling such polymers is then a measure of DNA which has covalently linked complementary sequences. By this assay, natural DNAs appear to contain short, relatively unstable bihelical regions following heat denaturation and cooling, in agreement with models based on other physical measurements.

Interaction of the Nucleation Processes Occurring at Adjacent Nucleation Sites

1993 ◽  
Vol 115 (4) ◽  
pp. 955-962 ◽  
Author(s):  
R. L. Judd ◽  
A. Chopra
Keyword(s):  
Experimental Investigation ◽  
Nucleation Site ◽  
Experimental Investigations ◽  
Nucleation Sites

An experimental investigation to explore the interaction between bubbles forming at adjacent nucleation sites is presented. The results obtained are consistent with the results of Calka’s and Knowles’ experimental investigations and confirm that nucleation site activation/deactivation, whereby a bubble growing at a nucleation site is able to promote/hinder the formation of a bubble at an adjacent nucleation site by depositing/displacing a vapor nucleus in the nucleation cavity, is instrumental in determining how a bubble forming at a nucleation site influences the nucleation of the subsequent bubble at an adjacent nucleation site.

Further Developments of Dropwise Condensation Theory

1979 ◽  
Vol 101 (4) ◽  
pp. 603-611 ◽  
Author(s):  
H. Tanaka
Keyword(s):  
Critical Size ◽  
Nucleation Site ◽  
Dropwise Condensation ◽  
Condensation Coefficient ◽  
Characteristic Parameters ◽  
Nusselt Numbers ◽  
Site Density ◽  
Nucleation Sites ◽  
Basic Equations ◽  
Nucleation Site Density

The high rates of heat transfer of dropwise condensation as well as its limits are explained on the basis of the behaviors of submicroscopic active drops. The expression for the substantial growth rate of a single drop valid down to the thermodynamic critical size is incorporated into a set of basic equations from [8] whose capability to describe the process of coalescence and growth of drops in dropwise condensation has been demonstrated in [9]. Consideration of the nondimensionalized forms of the basic equations with the aid of numerical analysis results in an expression of the Nusselt number for dropwise condensation in terms of a few characteristic parameters. Comparison of the predicted Nusselt numbers with available experimental data suggests that the condensation coefficient of water is around 0.2 provided the nucleation site density is infinitely high. Otherwise, if the condensation coefficient should be unity, we have to accept that the nucleation sites are fairly scattered.

Processing of Primary Silicon and Mg2Si Reinforced Hybrid Functionally Graded Aluminum Composites by Centrifugal Casting

2012 ◽  
Vol 710 ◽  
pp. 395-400 ◽  
Author(s):  
S. Raghunandan ◽  
Jasim Akber Hyder ◽  
T.P.D. Rajan ◽  
K. Narayan Prabhu ◽  
B.C. Pai
Keyword(s):  
Centrifugal Casting ◽  
Casting Process ◽  
Primary Silicon ◽  
Shrinkage Porosity ◽  
Functionally Graded ◽  
Al Alloy ◽  
Primary Si ◽  
The Difference ◽  
Silicon Particles

In the present investigation, FGMs of mono-dispersed in-situ primary Si and their hybrids with Mg2Si reinforcements have been fabricated by the centrifugal casting process using 390 commercial Al alloy. Hard primary silicon particles are formed during the solidification of the 390 alloy and Mg2Si reinforcements are formed by the addition of varying amount of magnesium into the A390 aluminium alloy. Owing to the difference in density both primary silicon and Mg2Si gets segregated towards the inner periphery during centrifugal casting. The size of the Mg2Siin-situreinforcement phase is relatively smaller and is distributed in the edges of primary silicon particles and also individually in the matrix. Thein-situMg2Si and primary silicon can significantly increase the hardness and strength of the inner periphery of the casting. Higher Mg contents have been observed to introduce significant porosity leading to poor castings. Addition of phosphorous to the melt has led to the modification and refinement of primary Si morphology and also helped in the reduction of shrinkage porosity. Maximum hardness of 167 BHN is observed towards the inner periphery of the 390Al-2.5%Mg added in-situ composite.

Selective Nucleation and Growth of Large Grain Polycrystalline GaAs

2005 ◽  
Vol 870 ◽  
Author(s):  
C. G. Allen ◽  
J. D. Beach ◽  
A. A. Khandekar ◽  
J. C. Dorr ◽  
C. Veauvy ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Nucleation Site ◽  
Site Formation ◽  
Organic Chemical ◽  
Subsequent Work ◽  
Nucleation Sites ◽  
Initial Nucleation ◽  
Electrochemically Deposited ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

AbstractA method for depositing large grained polycrystalline GaAs on lattice mismatched substrates through controlled nucleation and selective growth is presented. The process was developed on Si wafers. Nucleation site formation began with nanolithography to create submicron holes in photoresist on Si. Ga metal was electrochemically deposited into the holes. Subsequent arsine anneals converted the gallium deposits into GaAs. Photoluminescence and electron diffraction verified conversion to GaAs. Metal-Organic Chemical Vapor Deposition (MOCVD) enlarged the seed crystals to coalescence without creating additional nucleation sites within the patterned field. Having successfully demonstrated the approach, subsequent work has been directed at lower cost, alternative ways to define initial nucleation sites, such as, microcontact lithography and direct decomposition of triethyl gallium to Ga metal in the MOCVD chamber.

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